1. Field of the Invention
This invention relates to the field of invertible, pressure-responsive sealing caps for containers and more particularly to the field of such sealing caps for medical use wherein the sealing force progressively increases as the pressure within the container increases.
2. Discussion of the Background
Sealing cap and container combinations suitable for medical use present significant design challenges. In virtually all cases, it is required that the seal be reliable and predictable. Additionally, the cap and container combination must not only seal from the outset but also be capable of maintaining an effective seal even as the pressure differential across the cap increases. That is, in many applications and particularly in medical applications, the specimen in the container is often one (e.g., biohazardess materials such urine or tissue samples) that will ferment over time increasing the pressure within the container. Conversely, in many applications including medical ones, the sealed container may be subjected to reduced outside or ambient pressure (e.g., during transport by air freight) which has the same effect of increasing the relative pressure within the container. Additionally, large pressure differentials across the cap can occur even during transport or handling of the sealed container within the same facility (e.g., from a hospital examining room or nursing station via a pneumatic tube system to the hospital lab).
In these and other applications, it is important that the cap form an effective, initial seal and thereafter be capable of maintaining an effective seal as the pressure within the container increases relative to the outside or ambient pressure. With this in mind, the invertible, pressure-responsive sealing cap of the present invention was developed.